How can I get 8-bit waves?

Hello,

Just wondering if anyone can tell me a way to be able to use 8-bit waves (e.g., square, saw, triangle, etc.). I have magical 8-bit plug, but I was hoping for something with just a bit more potential for customization (it only has 4 wave choices, plus noise). Could there perhaps be a way to customize one of Garageband's built-in generators to sound 8-bit? Or is there a good free synth AU that can be customized to sound like 8-bit waves?